【Abstract】 Opportunistic infections (OIs) are critical criteria to distinguish patients with Acquired Immune Deficiency Syndrome (AIDS) from Human Immunodeficiency Virus (HIV) infected patients. And they are also dominant adverse events in HIV infected patients. To learn the types of HIV/AIDS related OIs, the risk factors and principles on diagnosis and treatment would effectively prevent the occurrence of OIs and retard the progress of diseases. Thus, these measures would help to improve patients’ life quality and decrease the mortality. Early initiation of antiretroviral therapy (ART) to restore cellular immunity is key method to prevent OIs and initiation of preventative antibiotics administration upon CD4 cell count also works. In conclusion, in severe immunosuppressive HIV infected patients, routine screening of OIs, early diagnosis and early intervention would improve the long term prognosis of patients.